Imaging unit of a camera for recording the surroundings with optics uncoupled from a circuit board

ABSTRACT

An imaging unit of a camera for recording the surroundings has an image sensor with a lens for the display of the surroundings on the image sensor. The image sensor and the lens are held by a carrier. The camera additionally has a circuit board and at least the signal and the supply lines of the image sensor arranged an the carrier. The image sensor is mounted an a carrier substrate, which similar to the lens, is arranged on the carrier at a distance from the circuit board, and has a flexible electrical connection to the circuit board.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. application Ser. No.12/324,011, filed Nov. 26, 2008, and claims priority of GermanApplication No.: 10 2007 057 172.2, filed on Nov. 26, 2007, and Europeanapplication No. 13157445.1 filed on Mar. 1, 2013.

BACKGROUND ART

The invention relates to an imaging unit of a camera for recording thesurroundings using an image sensor, to which one lens is allocated todisplay the surroundings on the image sensor, whereby the image sensoris held by a carrier, and with a circuit board arranged on said carrierand which has at least the signal and the supply lines of the imagesensor.

Such imaging units are used for various applications, e.g. forstereoscopic cameras, in order to control the movement of a mobiledevice based on the optically recording and processing of thesurroundings. In order to realize possible functions of the device, itspositioning, as well as avoiding any collisions when in motion, it isnecessary to constantly detect objects of the surroundings and theirdistance from the device, and to supply it for real-time processing.

The design of such an imaging unit of a camera regularly comprises anelectronic image sensor, to which a lens is allocated, which is adjustedto the respective application and also the sensor. The image sensor ismounted on a circuit board, on which signal lines, supply lines, and ifapplicable at least preliminary signal processing units are arranged.

The circuit board including the described structures is mounted on acarrier. The lens is arranged above the image sensor at a distance thatis necessary according to the optical system of the lens. It is mountedonto the carrier and the circuit board in such a way, so that the imagesensor is entirely encased, and light only impinges on the image sensorsthrough the lenses. If necessary, the lens has a separate housing forthis purpose.

The carrier and also its connections to the circuit board and the lensor its housing must meet various mechanical, thermal, chemical, andelectrical requirements for the different applications, whereby themechanical stability is to be ensured especially for the use in mobiledevices. For this reason, the carriers are usually made of metal.

Furthermore, the thermal expansion behavior of the carrier and that ofthe circuit board mounted permanently onto the carrier affects theimages taken by the camera. The different expansion coefficients of thetwo materials connected to each other lead to a shifting of the imagesensors relative to their lenses because of the heat created by theelectronic components when operating. Therefore, a loss of image qualityis detected, e.g. during extended operating, in particular for astereoscopic camera. In this way, the interferences are caused bydiffused light, which impinges on an image sensor through defectiveconnections between the carrier and the lens. The connections betweenthe carrier and the lens are mostly adhesive connections, which can tearaway from the carrier and the lens due to thermal expansions.

BRIEF SUMMARY OF THE INVENTION

Therefore, one aspect of the invention is to present an imaging unit ofa camera, which ensures temporarily stable optics of the imaging uniteven when undergoing thermal and mechanical stress.

Through the imaging unit as described in the following, any influence onits optical axis of the imaging unit in particular through the circuitboard or through the connection of the circuit board to the carrier isprevented when undergoing mechanical or thermal stress. Both the lensand the image sensor have a mechanical connection to the carrier only.

By uncoupling the optics from the circuit board, the position and theangle of the optical axis can be adjusted timewise in a very stablemanner. A drift of the optical axis of less than one pixel was detected,and that for both a mechanical shock impact of up to the 150-foldgravitational acceleration as well as operating temperatures rangingfrom −20° C. to 70° C. Such values could be obtained with a carrierhaving a thinner material than known carriers, so that particularly forhigh-valued materials expenditure could be minimized.

Furthermore based on the arrangement of the image sensor on a carriersubstrate and because of a flexible contacting between the circuit boardand the carrier substrate, the known electronic image sensor and lensescan be used. Thus depending on the design of the lens, image sensors canbe used with and without a housing, whereby the encased image sensorsmake the assembly of the camera outside a clean room environmentpossible.

The assembly of the lens onto the carrier also meets the camera'senhanced capacity to resist mechanical and thermal stress by arrangingthe lens above the image sensor using a lens fastener and in this waycreates an optically sealed hollow space around the image sensor, notincluding the optical path of the lens. This allows a mounting of thelens across a more extensive area supporting the compensation ofmechanical tension between the carrier and the lens fastener whilemaintaining a joint between the two components to be connected, andusing a flexible joint material to create the connection. In this way,any tearing of the connection can be prevented over a wide range ofthermal and mechanical stress.

Furthermore, the creation of a hollow space around the image sensor alsoallows the use of unencased components, as long as the performancerequirements of the image sensor demand such. Of course within thehollow space, encased components can be used just as well.

Further through creating a hollow space around the image sensor andthus, around the carrier substrate, it is possible to protect theflexible electrical connection between the image sensor and the circuitsof the circuit board from any damage by arranging the flexibleconnection inside the hollow space. For this purpose, the lens fastenercan have a penetration through which the conductor line extends into thehollow space. In order to realize a comparable connection at thislocation, there is also such a joint between the lens fastener and thecircuit board, as between the lens fastener and the carrier. This jointconnected with the circuit board is closed in the same manner as theother one with the carrier. For example, silicone also has the necessaryadhesive properties, as well as the required flexibility over a widerange of temperatures and the chemical resistance.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

In the following, the invention is to be described in greater detailusing an exemplary embodiment. The respective drawing FIG shows oneimaging unit of a camera in a cross section.

DETAILED DESCRIPTION

The camera comprises a plate-shaped carrier 3 with a rectangular base,which in the present exemplary embodiment is made from stainless steel.Carrier 3 has a pedestal 5, on which, on a flat carrier substrate 8 notshown in any more detail, an electronic image sensor 47 is supported.Each pedestal 5 has a support area slightly larger than the carriersubstrate 8.

A lens 9 is arranged using a lens fastener 11 above the image sensor 1and at a distance therefrom. One image sensor 7 and one lens 9 each forma single imaging unit 1. An optical system shall be referred to as lens9, comprising various optical elements, such as lenses or mirrors orothers, and displaying an object on the image sensor 7. The focus of thelens 9 can be adjusted in a fixed manner in various embodiments, knownas a fix-focus system, or is adjustable in the installed condition, sothat only following the installation of the lens 9 the focusedprojection of objects of certain distances is adjusted according to thethen existing distance between the lens 9 and the image sensor 7.

A circuit board 13 is arranged on the carrier 3 adjacent to the pedestal5 and at a distance thereto, which has an electronic circuit (not shownin greater detail) with integrated circuits, active and passive switchelements, and the necessary conductive pathways as well as conductorsfor conducting signals to and from the image sensors 7 (not shown ingreater detail) and for supplying power to the image sensors 7. Theelectronic circuit comprises, for example, the control of the imagingunit, for the recording of the images amongst other functions, the powersupply for the image sensors 7, or a unit for a preliminary processingof the signals received by the image sensors 7, in which the signals areprocessed for forwarding to a processing unit. For the signaltransmission between these components of the circuit board 13 and theimage sensor 7, and for supplying power to the image sensor 7, carriersubstrate 8 of an image sensor 7 is electrically connected to thecircuit board 13 via flexible connectors 15. As electrical connections15 of components, different embodiments are known through thesemi-conductor technology also suitable for this application such as,e.g. the connection using wire bridges. The image sensor 7 iselectrically contacted by the carrier substrate 8 (not shown in greaterdetail).

The lens fastener 11 of the imaging unit holds, protects, and positionsa lens 9, i.e. an optical system for the display the objects surroundingthe mobile device, and has the shape of a cuboid. The optical systemtherefore comprises several different optical elements according to therequirements for the imaging; however, for clarity purposes only onelens is shown. Standard embodiments of lenses 9 can also be used for thestereoscopic camera described.

The lens fastener 11 has a recess 17 at its side facing the carrier 3,whose base 18 is larger than the pedestal 5, on which the image sensor 7arranged on a carrier substrate 8 is supported. The lens fastener 11 isarranged on the carrier 3 in such a way, so that the recess 17 archesover the pedestal 5 and the image sensor 7 with a defined distancebetween the base 18 of the recess 17 and the image sensor 7.

The depth of the recess 17 is realized in such a way, so that the lensfastener 11 ends circumferentially with a joint above the carrier 3,without any further direct mechanical contact thereto. The lens fastener11 also is in a similar joint with the circuit board 13, which extendsthrough a low penetration 23 in the lens fastener 11 into the hollowspace formed by the recess 17 around the pedestal 5. The joint of thelens fastener 11 with the carrier 3 as well as the circuit board 13 isclosed circumferentially with a flexible joint material 25, so thatbased on the optically dense materials of the lens fastener 11 and thejoint material 25, the hollow space is realized in an optically sealedmanner, with the only possible radiation incidence through the lens 9positioned above the image sensor 7. The use of a flexible jointmaterial 25 makes the compensation of thermally caused stress betweenthe usually different materials of the carrier 3 and the lens fastener11 possible. The optical density does not only relate to visible lightbut can be related to all ranges of wavelengths that can be used for therecording of the surroundings in the respective application.

In the exemplary embodiment shown, the joint material 25 simultaneouslyfulfills the function of attaching the lens fastener 11 to the carrier 3by having adhesive properties. Alternatively, special means ofattachment may also be arranged at the lens fastener 11 and the carrier3.

The fixation of the precise lateral position of the lens fastener 11relative to the image sensor 7, and also its angular alignment isrealized by providing fastening means 27 at the lens fastener 11, eachof which extends into a recess 29 in the carrier 3. Through the amount,position, and design of the fastening means 27 and recesses 29, it ispossible to define an unambiguous allocation of a certain lens fastener11 relative to the imaging unit and to its exact position, so that itsassembly is also possible in at least a partially automated fashion.

One function of the fastening means 27 is the fixation of the lensfastener 11 in its position even under mechanical stress, as saidposition cannot be ensured for above described adhesion through theadhesive connection of lens fastener 11 and carrier 3 by means of aflexible material. For this purpose, the height of the fastening means27 and the depth of the recess 29 are chosen with such a size that adistance remains between the two bases 31, 33 of the fastening means 27and the recess 29 positioned opposite each other. Equally, the crosssections of fastening means 27 and the recess 29 are always of such asize, so that in this case again an intermediate space remains aroundthe fastening means 27 relative to the lateral wall of the recess 29.

The distance and intermediate space around the fastening means 27 isfilled with a curable mass, which is cured in the assembled state of theimaging unit shown. During the curing process, during which thefastening means 27 is immersed in the mass, the mass leads to a tensilestress on the fastening means 27 into the recess 29 as a consequence ofthe shrinking process associated with the curing, the below describedform of the fastening means 27 and as a consequence of the materialsalso below the fastening means 27.

In order to realize an engagement area at the fastening means 27 for theforces acting during the shrinking process and acting in the recess 29,the fastening means 27 is shaped in such a way, so that its crosssection, i.e. its virtual cross section positioned parallel to the base31 of the fastening means 27, increases towards the base 31. The shapeof the fastening means 27 can be realized, e.g. by a regular conicaldesign. However, other embodiments are also possible, e.g. an irregulartilted or one-sided cone as shown in FIG. 1, or a stepwise increase duea ledge, as long as the curable mass entirely encloses the fasteningmeans 27 using the mass during the immersion of the fastening means 27or during the subsequent filling of the intermediate space in the recess29, and it has an engagement area at the fastening means 27 through atensile force acting downward through the shrinking of the mass.

The invention claimed is:
 1. An imaging unit of a camera for recordingof surroundings, comprising: an image sensor, a lens to display thesurroundings on the image sensor, a carrier, a separate carriersubstrate for mounting the image sensor upon a first exterior surface ofthe carrier, and a circuit board arranged on the first exterior surfaceof the carrier laterally spaced apart from the separate carriersubstrate, the circuit board having at least signaling and supply linesfor the image sensor, wherein the image sensor is electrically contactedby the separate carrier substrate, and the separate carrier substrate iselectrically connected to the signaling and supply lines using flexibleelectrical connections, resulting in flexible contacting between thecircuit board and the separate carrier substrate, and further comprisinga lens fastener of optically dense material forming a hollow spacearound the image sensor together with the carrier, the lens fastenerbeing mounted on the carrier in an optically sealed manner, and whereinthe lens fastener has a penetration, through which the circuit boardextends into the hollow space, so that there is a joint between the lensfastener and the circuit board, and the joint is closed with a flexibleand optically dense joint material.
 2. The imaging unit of a cameraaccording to claim 1, wherein the lens fastener is arranged above thefirst exterior surface of the carrier circumferentially with a joint,and the joint is closed with a flexible and optically dense jointmaterial.
 3. The imaging unit of a camera according to claim 2, whereinthe lens fastener is fixated on the carrier through adhesion using thejoint material.
 4. The imaging unit of a camera according to claim 2,wherein the joint material comprises silicone.
 5. The imaging unit of acamera according to claim 1, wherein the lens fastener is fixated on thecarrier through adhesion using the joint material.
 6. The imaging unitof a camera according to claim 1, wherein the joint material comprisessilicone.
 7. The imaging unit of a camera according to claim 1, whereinfocus of the lens is adjustable.
 8. The imaging unit of a cameraaccording to claim 1, wherein the image sensor is encased.
 9. Theimaging unit of a camera according to claim 1 wherein the carriercomprises metal.
 10. An imaging unit of a camera for recording ofsurroundings, comprising: an image sensor, a lens to display thesurroundings on the image sensor, a carrier, a separate carriersubstrate for mounting the image sensor upon a first exterior surface ofthe carrier, and a circuit board arranged on the first exterior surfaceof the carrier laterally spaced apart from the separate carriersubstrate, the circuit board having at least signaling and supply linesfor the image sensor, wherein the image sensor is electrically contactedby the separate carrier substrate, and the separate carrier substrate iselectrically connected to the signaling and supply lines using flexibleelectrical connections, resulting in flexible contacting between thecircuit board and the separate carrier substrate, and further comprisinga lens fastener of optically dense material forming a hollow spacearound the image sensor together with the carrier, the lens fastenerbeing mounted on the carrier in an optically sealed manner, wherein thelens fastener has a fastening means extending into a recess in the firstexterior surface of the carrier, and a cross sectional area of thefastening means positioned parallel to a base of the recess increasestowards the base, the fastening means extends into the recess to anextent that there is an intermediate space between a base of thefastening means and the base of the recess, and a space of the recesssurrounding the fastening means including said intermediate space isfilled with a curable material.